Unveiling the interplay between sensory attenuation and fatigue: insights from healthy population and neurological disorders

Fatigue is a pervasive yet poorly understood phenomenon that affects both healthy individuals and patients with neurological disorders. This thesis investigates the role of predictive sensory mechanisms—particularly sensory attenuation (SA)—in the emergence and perception of fatigue. Across two parts, the work combines behavioural and clinical studies to examine how internal predictions shape body perception, effort, and movement. In Part 1, sensory attenuation was assessed in clinical populations with Parkinson’s disease and Functional Movement Disorder, as well as in healthy individuals varying in trait and state fatigue. The results demonstrate that pathological and trait fatigue are associated with impaired SA, suggesting an alteration in the brain’s ability to predict the sensory consequences of self-generated actions. These findings support and extend the Sensory Attenuation Model of Fatigue (SAF), highlighting the relevance of prediction errors in fatigue-related experiences. Part 2 broadens this framework by exploring how mental fatigue and multisensory integration influence body perception and predictive processes. Using a novel weight estimation task and vestibular modulation, the studies show that internal models governing body representation and sensory prediction are sensitive to both cognitive load and interoceptive signals. Together, these findings provide robust experimental support for the SAF model, showing that fatigue, both pathological and physiological, is linked to a breakdown in sensory attenuation mechanisms. This thesis offers new insights into the neurocognitive basis of fatigue and lays the groundwork for objective measures and interventions targeting sensory prediction mechanisms.